Lithium ionic energy storage element and method for making the same

ABSTRACT

A lithium ionic energy storage element comprises a positive electrode having a first current collector and a positive electrode active substance provided on the first current collector; a negative electrode having a second current collector and a negative electrode active substance provided on the second current collector, wherein the negative electrode active substance is a material selected from the group consisting of carbon-containing materials, Si alloy and Sn alloy; and an electrolyte, wherein the positive electrode active substance comprises a lithium ion donor including lithium peroxide, lithium oxide or the mixture thereof and a positive electrode frame active substance. The invention also relates to a method for making a lithium ionic energy storage element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a lithium ionic energy storage element, inparticular to a lithium ionic energy storage element comprising apositive electrode active substance including a lithium ion donor and apositive electrode frame active substance.

2. Description of the Related Art

In various energy storage technologies, lithium ionic batteries areregarded as a portable chemical power source with a high efficiency innext generation because they have advantages of high energy density,light weight and less pollution. Nowadays, the lithium ionic batteriesare widely used in the fields of digital cameras, smart phones andnotebooks. As the energy density of the lithium ionic battery isenhanced, the fields of use are extended. There is a higher need for theperformance of the lithium ionic battery as the requirement of highcapacity and long life of the lithium ionic battery for the mobileelectric equipment is increased

Typically, a lithium ionic battery comprises a negative electrode, apositive electrode and an electrolyte. The positive electrode activesubstance is not only used as an electrode material to take part in thechemical reaction, but also used as a lithium source. The positiveelectrode active substance is generally lithium metallic oxides whichcontain lithium atoms intercalated therein. Currently, lithium metallicoxides such as lithium cobalt oxide, lithium nickel oxide and lithiummanganese oxide are available commercially. However, the above lithiummetallic oxides cannot exhibit a proper combinative property of highinitial electrical capacity, high thermal stability and excellentelectrical capacity sustainability after a lithium ionic battery ischarged and discharged repeatedly.

The lithium ionic battery is limited by the capacity capacity (mA/g) ofthe positive electrode of the lithium metallic oxides, so that it cannotexhibit a higher capacitycapacity. Therefore, the lithium sources haveto be increased if it is desired to increase the capacity of the lithiumionic battery. Several methods were proposed, wherein one of the methodsis coating lithium metal used as lithium source on the negativeelectrode, and another method is forming lithium metal as a thirdelectrode on the negative electrode by electroplating. However, theabove two methods are difficult to perform and the coating andelectroplating film are not uniform because the lithium metal is veryactive.

Because lithium metal has disadvantages of safety and stability, thecurrent commercial lithium ion secondary battery is used a workingsystem having a positive electrode material containing lithium ions anda negative electrode material for intercalating lithium ions. In recentyears, the energy density of the lithium ion secondary battery has to beenhanced, because the electric devices have a large energy demand.However, the stability of the positive electrode material structure isnot high and the amount of lithium ions intercalation is not large, sothat the capacity per gram cannot be further enhanced.

Several materials, for example FeF₃, FePO₄ and V₂O₅ were proposed. Theabove materials are preferable to be the positive electrode material fora high energy density, because they have good electrical capacity and ahigher platform voltage. However, the above materials do not containlithium ions, so they have to combine with lithium metal. As a result,they would be only used in half cell tests but fail to be used in a fullcell.

Therefore, the inventor conducted researches according to the scientificapproach in order to improve and resolve the above drawback, and finallyproposed the present invention, which is reasonable and effective.

SUMMARY OF THE INVENTION

It is an object of present invention to provide a lithium ionic energystorage element. It can exhibit a high capacity by using a positiveelectrode active substance which comprises a lithium ion donor and apositive electrode frame active substance.

In order to achieve the above object, the present invention provides alithium ionic energy storage element comprising a positive electrodehaving a first current collector and a positive electrode activesubstance provided on the first current collector; a negative electrodehaving a second current collector and a negative electrode activesubstance provided on the second current collector, wherein the negativeelectrode active substance is a material selected from the groupconsisting of carbon-containing materials, Si alloy and Sn alloy; and anelectrolyte, wherein the positive electrode active substance comprises alithium ion donor including lithium peroxide, lithium oxide or themixture thereof and a positive electrode frame active substance.

The present invention also relates to a positive electrode activesubstance used in a lithium ionic energy storage element, the positiveelectrode active substance comprising a lithium ion donor and a positiveelectrode frame active substance, wherein the lithium ion donor includeslithium peroxide, lithium oxide or a combination of lithium peroxide andlithium oxide; and the positive electrode frame active substance is amaterial selected from the group consisting of anatase titanium dioxide,carbon-sulfur composite, carbon-containing materials and carbon fluorideor is lithium metallic oxides.

The present invention also relates to a method for making a lithiumionic energy storage element. At first, lithium peroxide, a positiveelectrode frame active substance, e.g. anatase titanium dioxide and abinder, e.g. PVDF are mixed with a predetermined weight ratio to form amixture, and the mixture is added into a dispersant, e.g.N-methyl-2-pyrrolidone to form a slurry. Next, the slurry is coating onan aluminum foil to form a film by a blade coater. The film is baked inan oven at a temperature of 80-90° C. to remove a solvent, and raise thetemperature to 120-130° C. for a period of time to form a positiveelectrode with lithium peroxide/anatase titanium dioxide. In order toincrease conductivity of lithium peroxide, conductive carbon, forexample super P carbon black, KS6 graphite or a combination thereof maybe added.

A lithium ionic energy storage element is formed by assembling thepositive electrode with lithium peroxide/anatase titanium dioxide, anegative electrode having a negative electrode active substance, e.g.graphitized mesocarbon microbeads (MCMB) and a porous separate stripinterposed between the positive electrode and the negative electrode,and an electrolyte, e.g. a concentration of 1M LiPF₆ dissolving in amixing solution of ethylene carbonate (EC) and diethyl carbonate (DEC)with mixing ratio 1:1 by volume is filled into the porous separatestrip.

Further, the present invention relates to a method for making a lithiumionic energy storage element. At first, lithium peroxide, a positiveelectrode frame active substance, e.g. carbon-sulfur composite and abinder, e.g. carboxymethyl cellulose (CMC) are mixed with apredetermined weight ratio to form a mixture, and the mixture is addedinto a dispersant, e.g. N-methyl-2-pyrrolidone to form a slurry. Next,the slurry is coating on an aluminum foil to form a film by a bladecoater. The film is baked in an oven at a temperature of 80-90° C. toremove a solvent, and raise the temperature to 120-130° C. for a periodof time to form a positive electrode with lithium peroxide/carbon-sulfurcomposite. In order to increase conductivity of lithium peroxide,conductive carbon, for example super P carbon black, KS6 graphite or acombination thereof may be added.

A lithium ionic energy storage element is formed by assembling thepositive electrode with lithium peroxide/carbon-sulfur composite, anegative electrode having a negative electrode active substance, e.g.hard carbon and a porous separate strip interposed between the positiveelectrode and the negative electrode, and an electrolyte, e.g. aconcentration of 1M lithium bis(trifluoromethanesulfonly)imidedissolving in a mixing solution of tetraethylene glycol dimethyl ether(TEGDME) and 1,3-dioxolane (DOL) with mixing ratio 1:1 by volume isfilled into the porous separate strip.

Compared to the conventional lithium ionic battery comprising lithiummetallic oxides, the lithium ionic energy storage element of the presentinvention comprises a lithium ion donor having lithium peroxide and/orlithium oxide and a positive electrode frame active substance, whereinlithium peroxide and/or lithium oxide can be decomposed to producelithium ions by electrochemical charging, and lithium ions intercalaterepeatedly in and out of the positive electrode frame active substanceand the negative electrode active substance in a full cell. The fullcell can exhibit a high capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a unit cell structure of a lithiumionic energy storage element an embodiment according to the invention.

FIG. 2 shows a first cycle curve of voltage against electric capacity ofa half cell of lithium peroxide charging/discharging of the invention.

FIG. 3 shows a second cycle and a third cycle curves of voltage againstelectric capacity of a half cell of lithium peroxidecharging/discharging of the invention.

FIG. 4 shows a first cycle curve of voltage against electric capacity ofa half cell of lithium peroxide charging/discharging under various ratioof a conductive carbon of the invention.

FIG. 5 shows cyclic voltammetry response of lithium peroxidecharging/discharging under various ratio of a conductive carbon of theinvention.

FIG. 6 shows the influent of voltage against electric capacity oflithium peroxide in the different current density.

FIG. 7(a) shows XRD pattern of TiO₂ synthetized from tetrabutyl titanateof the invention.

FIG. 7(b) shows XRD pattern of TiO₂ by simulation.

FIG. 8 shows a charging/discharging curve of prelithiation period ofLi₂O₂/TiO₂ half cell.

FIG. 9 shows a charging/discharging curve of subsequent cycles ofLi₂O₂/TiO₂ half cell.

FIG. 10 shows a charging/discharging curve of prelithiation period ofLi₂O₂/TiO₂ versus MCMB full cell.

FIG. 11 shows a charging/discharging curve of subsequent cycles ofLi₂O₂/TiO₂ versus MCMB full cell.

FIG. 12 shows a charge/discharge curve of prelithiation period ofLi₂O₂/TiO₂ versus MCMB with disassembling process of coin cell.

FIG. 13 shows a charge/discharge curve of subsequent cycles ofLi₂O₂/TiO₂ versus MCMB with disassembling process of coin cell.

FIG. 14 shows a charging/discharging curve of Li₂O₂ (30 wt. %) withcurrent density of 100 mA/g Li₂O₂ vs. Li metal of half cell.

FIG. 15 shows a charge/discharge curve of carbon-sulfur composite ofhalf cell.

FIG. 16 shows a charge/discharge curve of prelithiation period oflithium peroxide/carbon-sulfur composite vs. Li/Li⁺ of half cell.

DETAILED DESCRIPTION OF THE INVENTION

The technical content of invention will be explained in more detailbelow with reference to a few figures. However, the figures are intendedsolely for illustration and not to limit the inventive concept.

FIG. 1 shows a schematic view of a unit cell structure of a lithiumionic energy storage element an embodiment according to the invention.In the embodiment, the lithium ionic energy storage element comprises aplurality of unit cell structures 100, each unit cell structure 100comprises a porous separate strip 104 interposed between the positiveelectrode 106 and the negative electrode 108. The porous separate strip104 is coated with a binder 105 to enhance the binding of the cellstructure's 100 components to each other. The positive electrode 106 hasa first current collector 110 and a positive electrode active substance114 provided on the first current collector 110 and the negativeelectrode 108 has a second current collector 112 and a negativeelectrode active substance 116 provided on the second current collector112. The positive electrode active substance 114 comprises a lithium iondonor including lithium peroxide, lithium oxide or a combination thereofand a positive electrode frame active substance, e.g. anatase titaniumdioxide or carbon-sulfur composite. The carbon-sulfur composite has aweight ratio of carbon with sulfur is 0.4-1. In lithium peroxide/anatasetitanium dioxide system, the negative electrode active substance 116 maybe carbon-containing materials, e.g. graphitized mesocarbon microbeads(MCMB). In lithium peroxide/carbon-sulfur composite system, the negativeelectrode active substance 116 may be carbon-containing materials, e.g.hard carbon.

In the embodiment, the positive electrode active substance 114 used in alithium ionic energy storage element, the positive electrode activesubstance 114 comprising a lithium ion donor and a positive electrodeframe active substance, wherein the lithium ion donor includes lithiumperoxide, lithium oxide or a combination of lithium peroxide and lithiumoxide; and the positive electrode frame active substance is a materialselected from the group consisting of anatase titanium dioxide,carbon-sulfur composite, carbon-containing materials and carbon fluorideor is lithium metallic oxides.

The lithium ion donor of the invention may include but not be limited tolithium peroxide. For example, lithium oxide is also suitable to be thelithium ion donor. Alternative, lithium peroxide and lithium oxide aremixed for the use. In addition, the positive electrode frame activesubstance may use carbon-containing material, and thus both of thepositive electrode and negative electrode use carbon-containingmaterials to form lithium ion electric capacity accordingly. Carbonfluorides (CF_(x)) that have a high mass capacity ratio are suitable tobe the positive electrode frame active substance of the invention. Sialloy or Sn alloy that has a very high theoretical electrical capacityis also suitable to be negative electrode active substance 116 of theinvention.

An electrolyte that is suitable to a lithium ionic energy storageelement with lithium peroxide/anatase titanium dioxide system comprisesan inorganic compound such as LiPF₆, LiClO₄ or LiBF₄ and an organicsolvent that is a material selected from the group consisting ofethylene carbonate (EC) and diethyl carbonate (DEC). In addition, anelectrolyte comprises a concentration of 1M lithiumbis(trifluoromethanesulfonly)imide dissolving in a mixing solution oftetraethylene glycol dimethyl ether (EGDME) and 1,3-dioxolane (DOL) withmixing ratio 1:1 by volume that is suitable to a lithium ionic energystorage element with lithium peroxide/carbon-sulfur system.

In a charge/discharge mode of the unit cell structure 100 of theembodiment, lithium peroxide of the positive electrode active substance114 is decomposed to lithium ions and oxygen to intercalate intocarbon-containing materials of the negative electrode 108 when unit cellis charged, and the lithium ions located in the negative electrode 108diffuse to the positive electrode 106 and intercalate in the positiveelectrode active substance through the electrolyte when unit cell isdischarged.

At first, electric property of lithium peroxide is investigated. Thelithium ionic energy storage element of the present invention comprisesa lithium ion donor having lithium peroxide and/or lithium oxide and apositive electrode frame active substance, wherein lithium peroxideand/or lithium oxide can be decomposed to produce lithium ions byelectrochemical charging, and lithium ions intercalate repeatedly in andout of the positive electrode frame active substance and the negativeelectrode active substance in a full cell without containing Li ions.Because the conductivity of lithium peroxide is not high, a conductivecarbon may be added to enhance the conductivity of lithium peroxide.

The present invention provides a method for making a lithium ionicenergy storage element. At first, lithium peroxide, a positive electrodeframe active substance, e.g. anatase titanium dioxide, a conductivecarbon, for example super P carbon black, KS6 graphite or a combinationthereof and a binder, e.g. PVDF are mixed with a predetermined weightratio to form a mixture, and the mixture is added into a dispersant,e.g. N-methyl-2-pyrrolidone (NMP) to form a slurry. Next, the slurry iscoating on an aluminum foil to form a film by a blade coater. The filmis baked in an oven at a temperature of 80° C. for 6 hours to remove asolvent, and raise the temperature to 120° C. for 4-6 hours to form apositive electrode with lithium peroxide/anatase titanium dioxide.

A lithium ionic energy storage element is formed by assembling thepositive electrode with lithium peroxide/anatase titanium dioxide, anegative electrode having a negative electrode active substance, e.g.graphitized mesocarbon microbeads (MCMB) and a porous separate stripinterposed between the positive electrode and the negative electrode,and an electrolyte, e.g. a concentration of 1M LiPF₆ dissolving in amixing solution of ethylene carbonate (EC) and diethyl carbonate (DEC)with mixing ratio 1:1 by volume is filled into the porous separatestrip. The lithium ion donor of the invention may include but not belimited to lithium peroxide. For example, lithium oxide is also suitableto be the lithium ion donor. Alternative, lithium peroxide and lithiumoxide are mixed for the use. In addition, the positive electrode frameactive substance may use carbon-containing material, and thus both ofthe positive electrode and negative electrode use carbon-containingmaterials to form a lithium ion electric capacity accordingly. Carbonfluorides (CFx) that have a high mass capacity ratio are suitable to bethe positive electrode frame active substance of the invention. Si alloyor Sn alloy that has a very high theoretical electrical capacity is alsosuitable to be negative electrode active substance 116 of the invention.

Further, the present invention relates to a method for making a lithiumionic energy storage element. At first, lithium peroxide, a positiveelectrode frame active substance, e.g. carbon-sulfur composite, aconductive carbon, for example super P carbon black, KS6 graphite or acombination thereof and a binder, e.g. carboxymethyl cellulose (CMC) aremixed with a predetermined weight ratio to form a mixture, and themixture is added into a dispersant, e.g. N-methyl-2-pyrrolidone to forma slurry. Next, the slurry is coating on an aluminum foil to form a filmby a blade coater. The film is baked in an oven at a temperature of80-90° C. to remove a solvent, and raise the temperature to 120-130° C.for a period of time to form a positive electrode with lithiumperoxide/carbon-sulfur composite.

The lithium ion donor of the invention may include but not be limited tolithium peroxide. For example, lithium oxide is also suitable to be thelithium ion donor. Alternative, lithium peroxide and lithium oxide aremixed for the use. In addition, the positive electrode frame activesubstance may use carbon-containing material, and thus both of thepositive electrode and negative electrode use carbon-containingmaterials to form a lithium ion electric capacity accordingly. Carbonfluorides (CFx) that have a high mass capacity ratio are suitable to bethe positive electrode frame active substance of the invention. Si alloyor Sn alloy that has a very high theoretical electrical capacity is alsosuitable to be negative electrode active substance 116 of the invention.

A lithium ionic energy storage element is formed by assembling thepositive electrode with lithium peroxide/carbon-sulfur composite, anegative electrode having a negative electrode active substance, e.g.hard carbon and a porous separate strip interposed between the positiveelectrode and the negative electrode, and an electrolyte, e.g. aconcentration of 1M lithium bis(trifluoromethanesulfonly)imidedissolving in a mixing solution of tetraethylene glycol dimethyl ether(TEGDME) and 1,3-dioxolane (DOL) with mixing ratio 1:1 by volume isfilled into the porous separate strip.

(Performance Determination)

FIG. 2 shows a first cycle curve of voltage against electric capacity ofa half cell of lithium peroxide charging/discharging of the invention.FIG. 3 shows a second cycle and a third cycle curves of voltage againstelectric capacity of a half cell of lithium peroxidecharging/discharging of the invention. A half cell that is used for testis formed by assembling a positive electrode formed with mixing lithiumperoxide, super P carbon black and PVDF by weight ratio of 10:80:10; anda porous separate strip filled with an electrolyte, e.g. a concentrationof 1M LiPF₆ dissolving in a mixing solution of ethylene carbonate (EC)and diethyl carbonate (DEC) with mixing ratio 1:1 by volume. Conditionsof operation comprise charging/discharging current of 100 mA/g Li₂O₂ andcharging/discharging voltage of 2-4.6V.

FIG. 4 shows a first cycle curve of voltage against electric capacity ofa half cell of lithium peroxide charging/discharging under various ratioof a conductive carbon of the invention. A half cell that is used fortest is formed by assembling a positive electrode formed with mixinglithium peroxide, a conductive carbon (super P carbon black and KS6graphite with mixing ratio 1:1 by weight) and PVDF by weight ratio ofX:Y:10, wherein X=80, 60, 45, 30 and 10, and Y=10, 30, 45, 60 and 80;and a porous separate strip filled with an electrolyte, e.g. aconcentration of 1M LiPF₆ dissolving in a mixing solution of ethylenecarbonate (EC) and diethyl carbonate (DEC) with mixing ratio 1:1 byvolume. Conditions of operation comprise charging/discharging current of10 mA/g_(Li2O2) and charging/discharging voltage of 2-4.8V.

FIG. 5 shows cyclic voltammetry response of lithium peroxidecharging/discharging under various ratio of a conductive carbon of theinvention. A half cell that is used for test is formed by assembling apositive electrode formed with mixing lithium peroxide, a conductivecarbon (super P carbon black and KS6 graphite with mixing ratio 1:1 byweight) and PVDF by weight ratio of X:Y:10, wherein X:Y=10:80 and 30:60;and a porous separate strip filled with an electrolyte, e.g. aconcentration of 1M LiPF₆ dissolving in a mixing solution of ethylenecarbonate (EC) and diethyl carbonate (DEC) with mixing ratio 1:1 byvolume. Condition of operation comprises a scan rate of cyclicvoltammetry of 0.4 mV/s. The resultant current is 0 mA in the differentvoltage.

FIG. 6 shows the influent of voltage against electric capacity oflithium peroxide in the different current density. A half cell that isused for test is formed by assembling a positive electrode formed withmixing lithium peroxide, a conductive carbon (super P carbon black andKS6 graphite with mixing ratio 1:1 by weight) and PVDF by weight ratioof 30:60:10; and a porous separate strip filled with an electrolyte,e.g. a concentration of 1M LiPF6 dissolving in a mixing solution ofethylene carbonate (EC) and diethyl carbonate (DEC) with mixing ratio1:1 by volume. Conditions of operation comprise charging/dischargingcurrent of 10 mA/g Li₂O₂, 30 mA/g Li₂O₂ and 50 mA/g Li₂O₂ andcharging/discharging voltage of 2-4.8V. FIG. 7(a) shows XRD pattern ofTiO₂ synthetized from tetrabutyl titanate of the invention. FIG. 7(b)shows XRD pattern of TiO₂ by simulation. An error of degree (2θ) of XRDpattern of TiO₂ of FIG. 7(a) is obtained within 3% compared with XRDpattern of TiO₂ of FIG. 7(b).

The above tests show the various combinations of lithium peroxide, aconductive carbon and binder, and the influence of charging anddischarging of lithium peroxide in the different current density.However, lithium peroxide of the positive electrode is a functionalmaterial for use in one time, i.e. only may be decomposed by charging inone time. Therefore, another positive electrode active substance, forexample anatase titanium dioxide or carbon-sulfur composite is requiredto use for receiving Li ions that may diffuse to the positive electrodefrom the negative electrode in a discharging process.

The initial lithium peroxide may be decomposed to produce Li ions bycharging of the invention that is called as a charging period ofprelithiation, and Li ions diffuse to the positive electrode from thenegative electrode by discharging that is called as a discharging periodof prelithiation. The subsequent Li ions intercalate in and out in thepositive electrode and negative electrode that is called as a regularworking system.

Please refer to FIG. 8 and FIG. 9. FIG. 8 shows a charging/dischargingcurve of prelithiation period of Li₂O₂/TiO₂ half cell. FIG. 9 shows acharging/discharging curve of subsequent cycles of Li₂O₂/TiO₂ half cell.During charging period of prelithiation, lithium peroxide may be chargedto 4.8V against Li/Li⁺ by applying the current density of 50 mA/gLi₂O₂.During discharging period of prelithiation and subsequentcharging/discharging, TiO₂ may be charged and discharged at 1V-3Vagainst Li/Li⁺ by 0.1C (1C=335 mAh/g). The resultantcharging/discharging curves of half cells are shown in FIG. 8 and FIG.9. FIG. 8 shows a charging curve of Li₂O₂ with electric capacity of 365mA/gLi₂O₂ during charging period of prelithiation and a discharing curveof TiO₂ with two discharging platforms of 1.8V and 2.7V duringdischarging period of prelithiation, wherein the discharging platform of2.7V has electric capacity of 100 mAh/gTiO₂ that may be anoxidation-reduction reaction or regeneration of lithium peroxide, and itis regarded as a side reaction, i.e. the additional electric capacitymay not belong to TiO₂. Moreover, the resultant electric capacity may beabout 280 mAh/gTiO₂ after 100 mAh/gTiO₂ of the electric capacity of theside reaction is deducted from 380 mAh/gTiO₂.

Next, please refer to FIG. 10 and FIG. 11. FIG. 10 shows acharging/discharging curve of prelithiation period of Li₂O₂/TiO₂ versusMCMB full cell. FIG. 11 shows a charging/discharging curve of subsequentcycles of Li₂O₂/TiO₂ versus MCMB full cell. In the embodiment, anegative electrode is formed with mixing MCMB: super P carbon black: KSgraphite: binder=70:7.5:7.5:15 by weight; and a positive electrode isformed with mixing lithium peroxide, a conductive carbon, binder andtitanium dioxide by A/C ratio=1 versus weight of MCMB powder withcalculation of A/C ratio between Li₂O₂/TiO₂ cathode and MCMB anode asformulas:

Li₂O₂ vs MCMB: (372 mAh/g*0.5 g*0.7)/(410 mAh/g*xg)=1

x=0.4219 g Li₂O₂

TiO₂ vs MCMB: (350 mAh/g*0.5 g*0.7)/(335 mAh/g*yg)=1

y=0.4858 g TiO₂

According to the formulas based on the electric capacity of MCMB, theweight of each Li₂O₂, super P carbon black and KS graphite is 0.4219 g(22%) and the weight of PVDF is 0.1406 g (7%) and the weight of titaniumdioxide is 0.4858 g (27%). During charging period of prelithiation,lithium peroxide may be charged to 4.8V against MCMB by applying thecurrent density of 50 mA/gLi₂O₂. During discharging period ofprelithiation and subsequent charging/discharging, TiO₂ may be chargedand discharged at 0-3V against MCMB by 0.1 C (1 C=335 mAh/g). Theresultant charging/discharging curves of half cells are shown in FIG. 10and FIG. 11.

It could be found from the above experiments that Li ions prelithiationin the positive is successful. However, oxygen is produced in theprocess, and will affect the electrochemical performance. It isimportant to have an oxygen removal step for removing oxygen produced ina first cycle of charge and discharge the lithium ionic energy storageelement. In manufacturing a large scale of lithium ionic battery such asbattery with aluminum foil soft pack (pouch cell), a battery active stepis performed in a first cycle of charging and discharging the lithiumionic battery after filling the electrolyte into the porous separatestrip to form a solid electrolyte interphase (SEI) on the negativeelectrode, and the electrolyte decomposes in part at the same time.Next, the original electrolyte is withdrawn by evacuation, and a newelectrolyte is filled. Accordingly, a regular charging and dischargingthe lithium ionic battery can be performed. FIG. 12 shows acharge/discharge curve of prelithiation period of Li₂O₂/TiO₂ versus MCMBwith disassembling process of coin cell, and FIG. 13 shows acharge/discharge curve of subsequent cycles of Li₂O₂/TiO₂ versus MCMBwith disassembling process of coin cell. The effect of removing oxygenis not obvious from FIG. 12. However, there is not an acute decease inelectric capacity during the subsequent charge/discharge of TiO₂ thatcan prove the subsequent charge/discharge of TiO₂ is affected by theside reaction of the prelithiation discharging period. The source of theside reaction is the oxygen produced from the decomposition of lithiumperoxide during the prelithiation charging period.

In another embodiment, carbon-sulfur composite may be used for thepositive electrode frame active substance of the positive electrodeactive substance. Lithium peroxide is mixed with carbon-sulfur compositeto replace Li metal. A full cell is assembled by the positive electrodehaving the positive electrode active substance comprising lithiumperoxide and carbon-sulfur composite and the negative electrode havingthe negative electrode active substance comprising hard carbon. Beforeassembling a full cell, the electrochemical properties of lithiumperoxide and carbon-sulfur composite in ethers should be determinedBecause Li-sulfur battery uses ethers as an electrolyte, a half cellthat is used for test is formed by assembling a positive electrodeformed with mixing lithium peroxide, a conductive carbon and binder byweight ratio of 30:60:10; and a porous separate strip filled with anelectrolyte, e.g. a concentration of 1M lithiumbis(trifluoromethanesulfonly)imide dissolving in a mixing solution oftetraethylene glycol dimethyl ether (TEGDME) and 1,3-dioxolane (DOL)with mixing ratio 1:1 by volume. Conditions of operation comprisecharging/discharging current density of 100 mA/g Li₂O₂ vs. Li metal andcharging/discharging voltage of 2-4.3V in the embodiment, shown as FIG.14. The cut off voltage of charging is 4.3V. The half cell is chargedfor 9 hours by 100 mA/gLi₂O₂ after testing. It can be found thedecomposition of lithium peroxide in Li-sulfur battery electrolytesystem has the overpotential about 4.1V and the resultant electriccapacity about 980 mAh/gLi₂O₂.

FIG. 15 shows a charge/discharge curve of carbon-sulfur composite ofhalf cell. The carbon-sulfur composite of the half cell has a weightratio of carbon with sulfur is 0.4-1. Conditions of operation comprisecharging/discharging current density of 0.1 C (1 C=1672 mAh/gs) vs.Li/Li⁺ and charging/discharging voltage of 1.5V-3V in the embodiment,shown as FIG. 15.

FIG. 16 shows a charge/discharge curve of prelithiation period oflithium peroxide/carbon-sulfur composite vs. Li/Li⁺ of half cell. In theembodiment, a half cell that is used for test is formed by assembling apositive electrode formed with mixing lithium peroxide/carbon-sulfurcomposite, a conductive carbon and a binder dissolving in a dispersantof N-methyl-2-pyrrolidone; and a porous separate strip filled with anelectrolyte, e.g. a concentration of 1M lithiumbis(trifluoromethanesulfonly)imide dissolving in a mixing solution oftetraethylene glycol dimethyl ether (TEGDME) and 1,3-dioxolane (DOL)with mixing ratio 1:1 by volume. During charging period ofprelithiation, lithium peroxide may be charged with current density of100 mA/gLi₂O₂ to 4.3V against Li/Li⁺ by applying the current density of50 mA/gLi₂O₂. During discharging period of prelithiation and subsequentcharging/discharging, carbon-sulfur composite may be charged anddischarged against Li/Li⁺ by 0.1 C (1 C=1672 mAh/gs). The resultantcharging/discharging curves of half cells are shown in FIG. 16.

The lithium ionic energy storage element of the present inventioncomprises a lithium ion donor having lithium peroxide and/or lithiumoxide and a positive electrode frame active substance, wherein lithiumperoxide and/or lithium oxide can be decomposed to produce lithium ionsby electrochemical charging, and lithium ions intercalate repeatedly inand out of the positive electrode frame active substance and thenegative electrode active substance in a full cell. The full cell canexhibit a high capacity. The positive electrode frame active substanceof the positive electrode active substance can be a material selectedfrom the group consisting of anatase titanium dioxide, carbon-sulfurcomposite, carbon-containing materials and carbon fluoride, but notlimited to the above groups, as long as the materials that are stableand have excellent electric capacity are suitable as the positiveelectrode frame active substance. Even lithium metallic oxides may bethe positive electrode frame active substance to mix with lithiumperoxide and/or lithium oxide as the positive electrode active substancethat can exhibit a higher capacity than the full cell using lithiummetallic oxides only as the positive electrode active substance.

The invention is not limited to these embodiments, but variousvariations and modifications may be made without departing from thescope of the invention.

What is claimed is:
 1. A positive electrode active substance used in alithium ionic energy storage element, the positive electrode activesubstance comprising a lithium ion donor and a positive electrode frameactive substance, wherein the lithium ion donor includes lithiumperoxide, lithium oxide or a combination of lithium peroxide and lithiumoxide; and the positive electrode frame active substance is a materialselected from the group consisting of anatase titanium dioxide,carbon-sulfur composite, carbon-containing materials, carbon fluorideand—is lithium metallic oxides.
 2. A lithium ionic energy storageelement comprising: a positive electrode having a first currentcollector and a positive electrode active substance provided on thefirst current collector; a negative electrode having a second currentcollector and a negative electrode active substance provided on thesecond current collector, wherein the negative electrode activesubstance is a material selected from the group consisting ofcarbon-containing materials, Si alloy and Sn alloy; and an electrolyteinterposed between the positive electrode and the negative electrode,wherein the positive electrode active substance comprises a lithium iondonor including lithium peroxide, lithium oxide or a combination oflithium peroxide and lithium oxide and a positive electrode frame activesubstance.
 3. The lithium ionic energy storage element as claimed inclaim 2, wherein the positive electrode frame active substance of thepositive electrode active substance is a material selected from thegroup consisting of anatase titanium dioxide, carbon-sulfur composite,carbon-containing materials, carbon fluoride and lithium metallicoxides.
 4. The lithium ionic energy storage element as claimed in claim3, wherein the carbon-sulfur composite of the positive electrode frameactive substance has a weight ratio of carbon with sulfur is 0.4-1. 5.The lithium ionic energy storage element as claimed in claim 2, whereinthe positive electrode frame active substance is lithium metallicoxides.
 6. The lithium ionic energy storage element as claimed in claim2, wherein the positive electrode active substance contains conductivecarbon comprising super P carbon black, KS6 graphite or a combinationthereof.
 7. A method for making a lithium ionic energy storage elementcomprising steps: (a) mixing a lithium ion donor, a positive electrodeframe active substance and a binder with a predetermined weight ratio toform a mixture, and adding the mixture into a dispersant to form apositive electrode active substance, wherein the lithium ion donorincludes lithium peroxide, lithium oxide or a combination thereof; (b)coating the positive electrode active substance on an aluminum foil toform a film, and baking the film to form a positive electrode; and (c)forming a lithium ionic energy storage element by assembling thepositive electrode, a negative electrode having a negative electrodeactive substance and a porous separate strip interposed between thepositive electrode and the negative electrode, and filling anelectrolyte into the porous separate strip.
 8. The method as claimed inclaim 7, further comprising an oxygen removal step for removing oxygenproduced in a first cycle of charge and discharge the lithium ionicenergy storage element after filling the electrolyte into the porousseparate strip.
 9. The method as claimed in claim 7, wherein thepositive electrode frame active substance of the step (a) is a materialselected from the group consisting of anatase titanium dioxide,carbon-sulfur composite, carbon-containing materials and carbonfluoride.
 10. The method as claimed in claim 7, wherein the positiveelectrode frame active substance of the step (a) is lithium metallicoxides.
 11. The method as claimed in claim 7, further comprising addinga conductive carbon into the mixture of the step (a), wherein theconductive carbon is super P carbon black, KS6 graphite or a combinationthereof.
 12. The method as claimed in claim 7, wherein the binder in thestep (a) is polyvinylidene fluoride or carboxymethyl cellulose.
 13. Themethod as claimed in claim 7, wherein the negative electrode activesubstance of the step (c) is a material selected from the groupconsisting of graphitized mesocarbon microbeads, hard carbon, Si alloyand Sn alloy.
 14. The method as claimed in claim 7, wherein theelectrolyte of the step (c) is a concentration of 1M LiPF₆dissolving ina mixing solution of ethylene carbonate and diethyl carbonate; or aconcentration of 1M lithium bis(trifluoromethanesulfonly)imidedissolving in a mixing solution of tetraethylene glycol dimethyl etherand 1,3-dioxolane.
 15. The method as claimed in claim 7, wherein thedispersant of the step (a) is N-methyl-2-pyrrolidone.